The provision of a wear resistant insert in the face of the wrap surface of a knotting head is disclosed in U.S. Pat. No. 3,338,273 assigned to United Mattress Machinery Company, assignee of this application. The insert as disclosed in that patent is adjustably mounted in the segmental extension to provide for wires of different gauge. In operation the hardened insert applies the wrapping pressure as the free end of the wire is wrapped around the wire of the end loop. The wrapping pressure thus applied presses the portion of the end loop about which the end is being wrapped against the side of the radial slot opposite the wrap surface which results in rapid destructive wear so that frequent replacement of the entire knotting head is required. In order to rectify the aforesaid problem the hardened insert as disclosed in the aforesaid patent was replaced by a circular plug set into the end face of the extension and the end face of the body around the closed end of the radial slot containing a radial slot coinciding with the radial slot in the body. The plug was comprised of carbide steel and while extremely hard and resistant to wear it was relatively brittle so that the pressure developed cracked the plug at the closed end of the radial slot. The purpose of this invention is to provide means in both the wrap surface and the opposed surface of the radial slot which are wear resistant and will withstand the wrapping and wedging pressures developed during the knotting operation.